The invention relates to a method of constructing a skin for a member of a body, for example the skin of an aircraft wing.
It is known to produce wing skins from composite laminae. Such laminae are produced by a process known in the art as xe2x80x9claying upxe2x80x9d using, for example, carbon fibre tape. The tape is laid up in a multi-axial manner by a tape laying machine which provides a high degree of accuracy. The term xe2x80x9cMulti-axialxe2x80x9d means that alternate layers of tape will be laid by the machine in several different directions to produce a skin fabric having optimum strength in required directions. Commonly used directions for wing skin manufacture are 0xc2x0 (spanwise for the wing) xc2x145xc2x0, xe2x88x9245xc2x0 and 90xc2x0 (substantially chordwise).
In order for the skin to exhibit the correct characteristics when in position on, say, the completed wing, it is desirable that the laminae forming the skins be balanced. For example taking the case of a multi-axial skin having eight layers or plies a balanced lay-up from face to face could be as follows:
+45xc2x0 xe2x88x9245xc2x0, 90xc2x0, 0xc2x0, 0xc2x0, 90xc2x0, xe2x88x9245xc2x0, +45xc2x0
The laying up process is slow and a object of the present invention is to enable a balanced laminae arrangement to be constructed more quickly and easily than known hitherto.
According to a first aspect of the invention there is provided a method of constructing a skin for a member of a body such as an aircraft, the method comprising providing from a multi-axial fabric first and second pieces shaped to correspond respectively to shape of the member to be covered by the skin and to that of a similar member on the opposite side of the body, and inverting one of the pieces and placing it against the other to provide the skin.
By using the method in accordance with the invention, the placing of one of the pieces against the other produces the balanced laminae arrangement as described above. Also, a skin substantially double the thickness of each of the separate pieces can be made without having to produce the skin by a single laying up process, thus reducing production time.
The method may include, forming third and fourth pieces from multi axial fabric shaped to correspond respectively to the shape of the member to be covered by the skin and to the shape of the similar member on the opposite side of the body and inverting one of the third and fourth pieces and placing it on the other to form a skin for the similar member.
The method may further include forming the pieces from areas of the fabric which lie alongside each other. In that way, fabric wastage is minimised.
The areas of the fabric are preferably elongate and preferably extend substantially in a common longitudinal direction. In such a case, the method may include forming the multi-axial fabric with a layer of 0xc2x0 fibres extending in the longitudinal direction of said areas thereof.
Preferably, the method includes forming the multi-axial fabric by joining together edges of a plurality a fabrics made by a laying up process. In such a case, the method may include producing at least one of the first and second pieces in such a way that said piece is formed partly from one of said plurality of fabrics and partly from the other joined thereto. The joint between the two fabrics preferably runs in the one of the axial directions of the multi-axial fabric, for example in the 0xc2x0 direction.
In a preferred embodiment, the member is an aerofoil such as a wing on the body and the method include shaping the first and second pieces to correspond respectively to the plan view shape of the aerofoil and to that of a similar aerofoil on the opposite side of the body, inverting one of the pieces and placing it against the other to provide a skin for one of the aerofoils.
According to a second aspect of the invention there is provided a skin for a member of a body such as an aircraft, the skin being constructed in accordance with the method of the first aspect of the invention or any of the consistory clauses relating thereto.
According to a third aspect of the invention there is provided an aircraft aerofoil having a skin made in accordance with the method of the first aspect of the invention or any of the consistory clauses relating thereto.